Golden
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Golden clear sky chart from 2005-11-06 to 2024-02-05.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
35%
23218
6%
80401
5%
23139
37%
23139
10%
64124

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
19%
936
2%
4726
2%
926
20%
926
2%
4469
January11th to 20thNight
22%
795
13%
4399
2%
785
24%
785
4%
3308
January21st to endNight
22%
833
2%
4862
3%
814
25%
814
3%
4500
February1st to 10thNight
23%
738
4%
2582
3%
738
25%
738
6%
2238
February11th to 20thNight
30%
703
6%
2320
4%
700
33%
700
7%
1961
February21st to endNight
35%
592
9%
1776
7%
592
38%
592
10%
1472
March1st to 10thNight
30%
720
5%
2160
4%
720
31%
720
9%
1823
March11th to 20thNight
35%
720
8%
2102
5%
720
38%
720
13%
1690
March21st to endNight
34%
792
5%
2015
2%
792
35%
792
10%
1715
April1st to 10thNight
40%
720
6%
1800
3%
720
41%
720
12%
1477
April11th to 20thNight
36%
580
9%
1648
4%
580
39%
580
15%
1265
April21st to endNight
45%
491
7%
1571
6%
491
47%
491
15%
1157
May1st to 10thNight
51%
360
7%
1440
8%
360
54%
360
14%
1010
May11th to 20thNight
55%
354
9%
1330
11%
354
57%
354
21%
842
May21st to endNight
47%
388
5%
1358
3%
388
48%
388
17%
953
June1st to 10thNight
43%
360
1%
1260
0%
360
43%
360
15%
914
June11th to 20thNight
34%
360
0%
1147
0%
360
34%
360
11%
913
June21st to endNight
56%
360
0%
1080
0%
360
56%
360
24%
722
July1st to 10thNight
62%
350
2%
1114
0%
350
62%
350
29%
680
July11th to 20thNight
55%
348
6%
1229
3%
348
56%
348
25%
739
July21st to endNight
70%
394
12%
1488
17%
372
73%
372
36%
707
August1st to 10thNight
73%
358
14%
1424
22%
356
75%
356
28%
770
August11th to 20thNight
68%
391
20%
1459
24%
391
70%
391
33%
774
August21st to endNight
60%
638
17%
1826
14%
638
61%
638
28%
1192
September1st to 10thNight
50%
720
14%
1800
8%
720
51%
720
29%
1248
September11th to 20thNight
55%
720
14%
1898
10%
720
56%
720
25%
1345
September21st to endNight
44%
720
13%
1980
8%
720
47%
720
23%
1401
October1st to 10thNight
43%
720
10%
2065
8%
720
45%
720
19%
1492
October11th to 20thNight
35%
720
7%
2321
4%
720
38%
720
13%
1746
October21st to endNight
26%
792
5%
2574
4%
792
28%
792
9%
2109
November1st to 10thNight
20%
740
4%
2425
2%
740
22%
740
6%
2118
November11th to 20thNight
22%
917
4%
2817
2%
917
24%
917
5%
2503
November21st to endNight
25%
950
2%
2850
1%
950
25%
950
6%
2555
December1st to 10thNight
23%
950
4%
2850
3%
950
25%
950
7%
2499
December11th to 20thNight
19%
950
2%
3507
1%
949
20%
949
3%
3290
December21st to endNight
18%
1038
1%
5198
1%
1026
20%
1026
2%
4527

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
7%12%6%11%10%5%7%6%6%7%23%
78143
Night
5%12%6%12%10%5%7%6%6%7%24%
80655
TransparencyDay
58%12%12%12%5%
77857
Night
59%12%12%12%5%
80522
SeeingDay
13%16%31%26%11%2
14458
Night
11%12%31%32%13%1
23254

By Month

Percentage Cloud Cover NW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
314%12%23%17%5%6%5%445%
2219
11th to 20thDay
312%6%13%12%5%7%5%5%8%23%
2461
21st to endDay
6%19%12%18%10%5%5%5%5%5%9%
2794
February1st to 10thDay
313%7%12%13%7%10%7%6%7%16%
1472
11th to 20thDay
39%7%15%10%6%9%9%8%8%16%
1527
21st to endDay
19%6%15%13%11%9%8%6%6%15%
1480
March1st to 10thDay
213%8%13%13%7%8%7%7%7%16%
1800
11th to 20thDay
313%7%14%11%6%9%8%6%6%18%
1858
21st to endDay
317%9%14%12%6%7%7%7%5%12%
2340
April1st to 10thDay
6%16%8%14%11%6%7%7%5%6%14%
2160
11th to 20thDay
6%14%8%13%8%5%7%6%7%7%18%
2263
21st to endDay
8%18%7%10%8%46%6%7%7%19%
2385
May1st to 10thDay
10%15%6%11%8%46%6%7%7%21%
2520
11th to 20thDay
9%13%5%8%7%46%6%6%8%30%
2562
21st to endDay
16%13%5%9%7%45%5%6%7%23%
2917
June1st to 10thDay
18%12%5%9%8%46%6%6%7%20%
2700
11th to 20thDay
18%13%5%10%8%47%5%5%7%17%
2808
21st to endDay
10%8%48%8%5%7%7%6%8%28%
2880
July1st to 10thDay
10%7%37%8%46%5%7%9%35%
2808
11th to 20thDay
9%7%37%7%45%6%7%8%37%
2686
21st to endDay
5%5%36%6%35%5%6%9%48%
2741
August1st to 10thDay
7%6%47%8%46%6%7%7%39%
2507
11th to 20thDay
7%437%7%45%5%6%8%43%
2439
21st to endDay
9%8%37%7%47%6%6%8%34%
2526
September1st to 10thDay
8%9%48%8%45%46%8%35%
2160
11th to 20thDay
11%9%5%7%8%46%5%6%7%32%
2062
21st to endDay
10%11%5%10%9%46%5%6%7%27%
1980
October1st to 10thDay
9%11%5%10%8%5%7%5%5%8%27%
1891
11th to 20thDay
6%11%6%11%7%5%8%7%7%7%24%
1638
21st to endDay
5%17%5%10%9%6%8%7%7%7%19%
1782
November1st to 10thDay
5%15%8%14%13%5%8%7%7%6%13%
1651
11th to 20thDay
311%8%14%12%7%9%8%7%7%15%
1342
21st to endDay
412%7%12%14%8%9%7%8%6%14%
1330
December1st to 10thDay
412%7%14%14%7%9%6%6%6%15%
1330
11th to 20thDay
217%8%25%15%8%7%5%446%
1682
21st to endDay
214%9%18%15%8%6%6%6%5%11%
2442
January1st to 10thNight
317%13%24%14%6%6%4346%
4726
11th to 20thNight
312%5%14%11%5%7%10%8%7%18%
4466
21st to endNight
6%25%13%17%10%47%4447%
4862
February1st to 10thNight
313%7%14%13%7%9%8%7%6%13%
2582
11th to 20thNight
213%6%13%10%6%8%6%8%8%19%
2318
21st to endNight
29%6%13%13%7%9%7%8%7%20%
1776
March1st to 10thNight
310%7%14%11%6%9%7%8%7%20%
2160
11th to 20thNight
211%5%10%8%6%7%8%9%8%25%
2101
21st to endNight
212%6%10%9%5%7%9%9%10%22%
2015
April1st to 10thNight
411%6%9%7%5%7%8%8%8%25%
1800
11th to 20thNight
411%5%10%8%46%7%8%8%28%
1648
21st to endNight
5%10%47%7%37%6%8%9%34%
1571
May1st to 10thNight
6%10%47%7%36%6%7%9%34%
1440
11th to 20thNight
6%6%36%6%46%6%7%10%41%
1330
21st to endNight
14%7%36%6%35%5%7%7%36%
1358
June1st to 10thNight
14%10%37%5%46%5%6%8%33%
1260
11th to 20thNight
12%10%410%9%5%6%7%6%7%24%
1147
21st to endNight
6%6%25%7%45%6%8%12%39%
1080
July1st to 10thNight
5%6%35%5%36%6%5%7%49%
1147
11th to 20thNight
6%5%26%5%35%6%6%8%48%
1271
21st to endNight
4313435%46%8%58%
1576
August1st to 10thNight
44245%35%5%7%8%52%
1432
11th to 20thNight
5%4234346%7%8%54%
1459
21st to endNight
6%5%245%36%6%8%10%45%
1826
September1st to 10thNight
8%8%35%5%45%5%6%6%45%
1800
11th to 20thNight
10%7%35%5%5%5%6%5%7%42%
1898
21st to endNight
11%7%36%6%45%7%7%9%38%
1980
October1st to 10thNight
6%8%48%8%46%6%7%8%35%
2065
11th to 20thNight
7%10%49%8%45%6%7%8%31%
2321
21st to endNight
5%13%6%11%9%5%7%6%7%9%22%
2574
November1st to 10thNight
8%15%8%12%12%6%6%6%6%6%14%
2425
11th to 20thNight
414%6%13%12%8%9%7%6%7%14%
2817
21st to endNight
414%8%15%13%7%8%7%6%6%11%
2850
December1st to 10thNight
5%13%7%14%14%8%8%8%6%6%11%
2850
11th to 20thNight
218%8%21%16%8%7%6%5%45%
3510
21st to endNight
313%8%20%15%9%8%5%5%411%
5214

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
83%9%431
2219
11th to 20thDay
60%8%11%9%8%5%
2485
21st to endDay
76%11%7%42
2794
February1st to 10thDay
67%12%10%6%4
1472
11th to 20thDay
62%17%11%8%21
1535
21st to endDay
66%13%9%6%5%1
1480
March1st to 10thDay
64%13%12%6%5%
1800
11th to 20thDay
63%13%10%11%3
1858
21st to endDay
72%12%9%5%2
2340
April1st to 10thDay
69%12%12%7%1
2160
11th to 20thDay
63%11%13%11%2
2263
21st to endDay
63%13%13%10%2
2385
May1st to 10thDay
60%13%15%10%2
2520
11th to 20thDay
51%13%17%16%4
2566
21st to endDay
59%11%14%12%3
2918
June1st to 10thDay
61%11%11%12%31
2700
11th to 20thDay
66%12%10%9%3
2808
21st to endDay
51%12%15%16%6%1
2880
July1st to 10thDay
43%11%15%18%11%1
2733
11th to 20thDay
44%11%15%18%12%
2605
21st to endDay
33%9%14%29%15%1
2589
August1st to 10thDay
40%11%16%23%10%1
2490
11th to 20thDay
35%10%19%24%12%1
2439
21st to endDay
45%12%13%21%7%1
2526
September1st to 10thDay
46%10%17%20%6%1
2160
11th to 20thDay
50%11%15%19%6%
2062
21st to endDay
55%10%15%15%4
1980
October1st to 10thDay
53%12%14%17%4
1891
11th to 20thDay
56%15%14%13%2
1638
21st to endDay
60%14%13%9%3
1782
November1st to 10thDay
71%13%7%7%2
1651
11th to 20thDay
68%15%8%5%4
1342
21st to endDay
66%16%9%441
1330
December1st to 10thDay
68%11%10%10%2
1330
11th to 20thDay
80%7%7%41
1684
21st to endDay
62%18%12%43
2442
January1st to 10thNight
83%9%4211
4726
11th to 20thNight
59%11%10%10%8%3
4504
21st to endNight
82%7%6%31
4862
February1st to 10thNight
70%11%9%6%31
2582
11th to 20thNight
64%14%11%9%2
2320
21st to endNight
62%12%11%9%5%1
1776
March1st to 10thNight
62%14%11%8%4
2160
11th to 20thNight
54%16%15%11%5%
2102
21st to endNight
56%19%13%7%4
2015
April1st to 10thNight
53%18%16%10%2
1800
11th to 20thNight
50%14%17%13%5%
1648
21st to endNight
46%16%18%15%4
1571
May1st to 10thNight
45%15%19%16%5%
1440
11th to 20thNight
36%14%22%23%5%
1330
21st to endNight
45%13%17%20%5%
1358
June1st to 10thNight
47%14%12%21%41
1260
11th to 20thNight
57%14%14%11%4
1147
21st to endNight
35%15%20%24%5%1
1080
July1st to 10thNight
32%11%18%25%12%2
1114
11th to 20thNight
34%11%20%24%11%
1229
21st to endNight
22%8%17%36%16%1
1488
August1st to 10thNight
26%13%19%29%12%1
1424
11th to 20thNight
25%11%23%29%12%
1459
21st to endNight
33%14%18%27%9%
1826
September1st to 10thNight
39%10%18%26%7%
1800
11th to 20thNight
40%13%18%19%10%1
1898
21st to endNight
41%13%21%18%7%
1980
October1st to 10thNight
45%13%18%20%5%
2065
11th to 20thNight
50%15%17%15%3
2321
21st to endNight
60%14%13%10%2
2574
November1st to 10thNight
72%10%8%6%4
2425
11th to 20thNight
72%11%8%5%3
2817
21st to endNight
73%11%7%5%3
2850
December1st to 10thNight
71%10%9%8%2
2850
11th to 20thNight
82%9%432
3507
21st to endNight
69%15%8%6%2
5214

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
8%12%34%30%11%5%
180
11th to 20thDay
6%18%33%31%12%1
180
21st to endDay
6%19%37%26%8%4
198
February1st to 10thDay
11%22%42%17%7%2
168
11th to 20thDay
6%18%39%29%7%1
259
21st to endDay
414%41%29%10%2
346
March1st to 10thDay
7%24%39%19%9%2
420
11th to 20thDay
10%21%36%21%10%2
420
21st to endDay
15%19%31%24%10%2
462
April1st to 10thDay
13%22%35%22%8%
420
11th to 20thDay
11%23%32%22%10%3
412
21st to endDay
13%22%30%22%10%3
420
May1st to 10thDay
19%18%27%23%11%2
423
11th to 20thDay
15%10%26%29%17%3
533
21st to endDay
18%11%22%29%17%3
679
June1st to 10thDay
20%16%28%25%10%1
630
11th to 20thDay
22%16%29%22%9%1
738
21st to endDay
12%15%28%31%12%2
810
July1st to 10thDay
14%13%27%31%13%2
728
11th to 20thDay
13%14%29%28%14%2
604
21st to endDay
6%15%33%28%15%4
487
August1st to 10thDay
9%11%30%32%14%3
447
11th to 20thDay
11%14%32%30%11%2
437
21st to endDay
12%18%26%30%12%2
495
September1st to 10thDay
15%19%33%21%10%3
450
11th to 20thDay
15%14%30%30%10%1
450
21st to endDay
16%20%34%20%8%1
450
October1st to 10thDay
16%14%30%27%11%1
450
11th to 20thDay
14%19%32%23%11%1
288
21st to endDay
16%17%35%24%6%2
297
November1st to 10thDay
12%16%39%23%9%2
259
11th to 20thDay
10%21%39%24%6%1
180
21st to endDay
7%21%36%22%8%7%
180
December1st to 10thDay
9%12%35%31%9%4
180
11th to 20thDay
6%16%44%25%9%
180
21st to endDay
6%14%32%35%11%3
198
January1st to 10thNight
12%17%38%26%7%1
950
11th to 20thNight
10%13%40%28%8%1
805
21st to endNight
8%14%40%26%10%1
836
February1st to 10thNight
9%16%38%24%10%1
738
11th to 20thNight
10%14%34%34%9%1
704
21st to endNight
7%9%34%32%17%2
592
March1st to 10thNight
7%14%37%29%12%
720
11th to 20thNight
7%15%35%33%10%
720
21st to endNight
9%14%32%29%15%2
792
April1st to 10thNight
7%11%29%36%16%1
720
11th to 20thNight
10%11%34%34%11%1
580
21st to endNight
8%15%25%36%14%1
491
May1st to 10thNight
9%9%22%38%22%
360
11th to 20thNight
9%5%24%38%22%1
354
21st to endNight
15%8%21%34%20%2
389
June1st to 10thNight
18%7%26%35%13%1
360
11th to 20thNight
15%12%28%29%16%1
360
21st to endNight
9%6%23%41%20%
360
July1st to 10thNight
10%5%18%42%24%
350
11th to 20thNight
10%6%24%40%20%1
348
21st to endNight
7%416%47%26%1
394
August1st to 10thNight
7%312%44%34%1
358
11th to 20thNight
7%5%16%42%29%2
391
21st to endNight
8%8%19%41%23%1
638
September1st to 10thNight
13%8%23%35%19%3
720
11th to 20thNight
13%8%19%37%20%4
720
21st to endNight
15%10%25%33%15%1
720
October1st to 10thNight
12%9%28%37%14%1
720
11th to 20thNight
13%11%32%33%10%1
720
21st to endNight
13%16%37%24%10%1
792
November1st to 10thNight
18%16%37%23%6%1
740
11th to 20thNight
11%18%39%25%6%
917
21st to endNight
11%14%35%29%9%1
950
December1st to 10thNight
11%12%39%27%10%1
950
11th to 20thNight
12%13%37%29%9%
950
21st to endNight
10%13%40%28%9%1
1045
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Copyright 2024 Attilla Danko


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